HILL : GEOLOGY OF THE ISTHMUS OF PANAMA. 243 



Carl Sapper * has described a system of pudding-stones, sands, and red 

 or yellow clays as the Todos Santos beds. 



The physiographic significance of the early Mesozoic Red Beds has 

 never been interpreted, even in the United States, where they are so 

 abundant. In general, however, from the shallow water nature of the 

 sediments, the scarcity of marine life, and the presence of plants, they 

 indicate the coexistence of extensive areas of near-by land. Xo Jurassic 

 rocks are reported from Central America. 



The Cretaceous Strata. — The present area of the Republic of Mexico 

 was mostly beneath the sea in Cretaceous times, but, as we shall show in 

 the subsequent discussion, it is doubtful if the whole of the country was 

 entirely submerged at any one time during this epoch. 



Cretaceous sediments and limestones are found in the Republic of 

 Guatemala on the north side of the granitic proto-ranges. As I have 

 shown in this paper, there is one small outcrop in Costa Rica. From 

 Costa Rica westward Cretaceous deposits have not been reported any- 

 where in the Isthmian region, nor are they apt to occur at the surface 

 until we reach the Andean and Caribbean folds of Northern Colombia 

 and Venezuela. Prof. A. Agassiz has mentioned one Cretaceous species 

 from the Isthmus. 2 They are extensively developed in three distinct 

 provinces of the South American continent : along the Pacific border, 

 near the Caribbean coasts of Colombia and Venezuela, and in Trinidad, 

 and south of the Orinoco in Brazil. Cretaceous rocks also outcrop in the 

 islands of the Greater Antilles, Jamaica, Santo Domingo, and Cuba. 



The Cretaceous formations of the Pacific coast of South America 

 lie along the upturned flanks of the Andes. The exact relations and 

 limitations in distribution of its faunas have not been thoroughly es- 

 tablished or compared with those of the other South American provinces ; 

 but from such figures as have been published of its species, we are in- 

 clined to believe that it shows the same great dissimilarity to that of 

 the eastern lying provinces of Brazil as does the Cretaceous of our own 

 North American Paci6c coast to that of the Atlantic and Gulf region. 

 The Cretaceous of Colombia and Venezuela east of the Magdalena River, 

 as has been fragmentarily published by Boussingault, d'Orbigny, and 

 Karsten, certainly shows a great dissimilarity in species to that of the 

 strictly Andean province. This is a field, however, which needs explora- 

 tion by some one familiar with American Cretaceous paleontology. The 

 difference between the Brazilian and Andean Cretaceous is even more 

 striking. 



1 See footnote 1, p. 239. 2 Loc. cit., page 173. 



